diff --git a/lib/shoulda/matchers/active_record/validate_presence_of_matcher.rb b/lib/shoulda/matchers/active_record/validate_presence_of_matcher.rb
index e792461a..088a1cd8 100644
--- a/lib/shoulda/matchers/active_record/validate_presence_of_matcher.rb
+++ b/lib/shoulda/matchers/active_record/validate_presence_of_matcher.rb
@@ -47,7 +47,8 @@ module Shoulda # :nodoc:
         end
 
         def collection?
-          if reflection = @subject.class.reflect_on_association(@attribute)
+          if @subject.class.respond_to?(:reflect_on_association) &&
+              reflection = @subject.class.reflect_on_association(@attribute)
             [:has_many, :has_and_belongs_to_many].include?(reflection.macro)
           else
             false
diff --git a/spec/shoulda/active_record/validate_presence_of_matcher_spec.rb b/spec/shoulda/active_record/validate_presence_of_matcher_spec.rb
index 9439f9cd..7fd6f792 100644
--- a/spec/shoulda/active_record/validate_presence_of_matcher_spec.rb
+++ b/spec/shoulda/active_record/validate_presence_of_matcher_spec.rb
@@ -19,6 +19,23 @@ describe Shoulda::Matchers::ActiveRecord::ValidatePresenceOfMatcher do
     end
   end
 
+  context "a required attribute on a class using ActiveModel::Validations" do
+    before do
+      define_active_model_class("Example", :accessors => [:attr]) do
+        validates_presence_of :attr
+      end
+      @model = Example.new
+    end
+
+    it "should require a value" do
+      @model.should validate_presence_of(:attr)
+    end
+
+    it "should not override the default message with a blank" do
+      @model.should validate_presence_of(:attr).with_message(nil)
+    end
+  end
+
   context "an optional attribute" do
     before do
       @model = define_model(:example, :attr => :string).new
@@ -29,6 +46,16 @@ describe Shoulda::Matchers::ActiveRecord::ValidatePresenceOfMatcher do
     end
   end
 
+  context "an optional attribute on a class using ActiveModel::Validations" do
+    before do
+      @model = define_active_model_class("Example", :accessors => [:attr]).new
+    end
+
+    it "should not require a value" do
+      @model.should_not validate_presence_of(:attr)
+    end
+  end
+
   context "a required has_many association" do
     before do
       define_model :child
diff --git a/spec/support/model_builder.rb b/spec/support/model_builder.rb
index 3c13b241..50a794a6 100644
--- a/spec/support/model_builder.rb
+++ b/spec/support/model_builder.rb
@@ -42,6 +42,18 @@ module ModelBuilder
     define_constant(class_name, ActiveRecord::Base, &block)
   end
 
+  def define_active_model_class(class_name, options = {}, &block)
+    define_constant(class_name, Object) do
+      include ActiveModel::Validations
+
+      options[:accessors].each do |column|
+        attr_accessor column.to_sym
+      end
+
+      class_eval(&block) if block_given?
+    end
+  end
+
   def define_model(name, columns = {}, &block)
     class_name = name.to_s.pluralize.classify
     table_name = class_name.tableize